The accusations, which were first published in the paper on Wednesday, centre on a 1996 programme called The Connection.

The documentary, produced by the TV company Carlton, purported to penetrate the undercover world of drug smuggling between Colombia and Britain.

Its producer, Marc de Beaufort, has denied any wrong-doing.

Thursday's edition of the newspaper repeats allegations that some scenes in the film were faked.

Guardian editor, Alan Rusbridger: "It's about time methods were exposed"

It also claims that executives at Carlton Television were told six days before transmission that the programme was flawed.

On of the executives involved has denied the accusation.

Among the documentary's contentious scences are one in which a "drug courier" is seen swallowing scores of packages of heroin, then taking a plane to London and slipping into Britain.

But the Guardian says the packages did not contain heroin. It claims the plane ticket for the "drugs mule" was paid for by the producer and that when he arrived at Heathrow airport he did not get through customs, as was suggested, but was deported.

It also says that the mule's continuous journey from Bogata to London was filmed in two stages, six months apart.

Producer Marc de Beaufort says there was no misrepresentation

One man described as the "number three" in an infamous drugs ring was actually a retired bank cashier with low level drug connections, the paper claims.

In its Thursday edition, the paper says that the Independent Television Commission, the government-run TV watchdog, has launched an inquiry following its allegations.

Guardian editor Alan Rusbridger says the case is not unique.

"There's a pressure on people to come up with exciting, glamorous stories and to cut corners," he said.

"It think that it's about time that somebody exposed some of the methods that have been going on."

But Mr de Beaufort has denied the accusations. He says he believes the participants were genuine drug dealers. However, he does admit using devices such as editing to make two journeys look like one.